A substance with high UVA and UVB spectral absorption stability, high heat absorption, and insulation capabilities is desired for a number of applications, including wire and cable insulation, wood preservatives, paints, roofing materials, composite building materials, thermoplastics, motor vehicle and aircraft parts, textiles, rubber, and sunscreens, among numerous other uses. With greater public awareness regarding issues of health and the environment, a complex, non-toxic to humans and mammals, derived from natural-based, earth-derived ingredients is preferred in these applications over that of a substance that is potentially harmful to human and/or environmental health. Other ZnO complexes (dispersions) utilize either synthetic or toxic (or both) additives/coatings in order to stabilize the complex. The present application and associated invention describes a ZnO complex which utilizes neither toxicity or are synthetic (such as silicones).
It is instructive to consider the potential damage that UVA and UVB radiation poses to car dashboards and parts of aircraft. The sun's damaging rays are apt to cause these areas on vehicles to crack, crumble, or become otherwise damaged over time, thereby impeding their efficacy and reducing their aesthetic appeal.
Also, wires and cables for outdoor use require some form of insulation or outer coating to prevent their degradation as a result of the heat and ultraviolet radiation produced by the sun. Today, polymers and rubber are primarily used for insulation; however, these insulating products are subject to cracking and may not offer sufficient heat, moisture, electrical or thermal insulating properties as well as UVA/UVB protection.
Using a product that provides high UVA/UVB protection for textile applications such as clothing, window shades, woven and non-woven fabrics could be manufactured with metal oxide materials that include heat and ultraviolet ray absorption properties as well as improved sun protection factors that could help keep wearers free from sunburn and allow for users to obtain products that remain stable in the outdoors for longer time durations.
The present application and associated invention also can be applied to wood preservatives, composite building materials, roofing materials, and even in mirrored glass to protect these products from the harmful effects of UVA and UVB radiation, thus prolonging their efficaciousness in an unobtrusive, relatively inexpensive manner.
Carbon black is a well-known product with similar properties to the disclosed composition of matter: UVA/UVB stability, pigmentation, and heat absorption, are all useful properties. Carbon black is commonly used in rubbers and tires as a filler and reinforcer, in plastics, and in high performance coatings. However, because carbon black is commonly provided as a dust or powder, it poses some health risks, including possible respiratory and eye irritation upon exposure. It is also classified by the International Agency for Research on Cancer as a group 2B carcinogen, indicating that it is possibly carcinogenic to humans. Furthermore, carbon black is not non-endocrine disrupting or non-toxic and can pose some risk to the environment if not disposed of properly. Also, carbon black is limited in its uses because it cannot be applied in products such as sunscreens and cosmetics to protect humans from the sun's dangers. It also does not possess the anti-microbial properties of the present composition provided in this disclosure.
The present disclosure provides a zinc oxide based complex comprising natural-based, earth-derived ingredients exhibiting unparalleled UVA and UVB spectral absorption stability, high SPF values as measured in-vitro, as well as anti-microbial, insulative, and heat absorption properties. Because the complex is derived from natural-based, earth-derived ingredients and substances non-toxic to humans and mammals, it is highly desirable for use in a number of applications where other compounds cannot or should not be used as they may endanger the environment and/or human health.
The present disclosure also provides for a new zinc-oxide based composition of matter in which distilled water is adjusted to a pH of 10 or greater using a buffering agent such as ammonium hydroxide, L-arginine, or sodium hydroxide. Micronized zinc oxide particles are then added to the buffered water while ensuring that the pH remains above 10. The dispersion of the zinc oxide through the buffered water then occurs as the zinc oxide particles disperse in a continuous phase. Normally within 24 hours, a zinc oxide complex is formed which can create a pinhole free thin film layer with high SPF values, ranging from at least 100 nm up to 460 nm when measured in-vitro using the Labsphere UV 2000S Ultraviolet Transmittance Analyzer, available from Labsphere of North Sutton, N.H. and exhibits unparalleled UVA and UVB spectral absorption stability.
In one embodiment an ammonium hydroxide (NH4OH) buffer solution is added to distilled water to attain a pH of preferably between 10.0 and 11.0 before adding the zinc oxide particles to pH adjusted distilled water to avoid zinc hydroxide formation. Hydroxide formation is minimized by continuously adding zinc oxide and not allowing the pH to drop below 10.0. Adding more ammonium hydroxide buffer solution to raise the pH, if the extra addition of zinc oxide reduces the pH, is critical to assure no further reduction of the pH. Within 24 hours the zinc oxide solution pH increases from about 10.0 to about 10.4.
In another embodiment any amine, preferably the amino acid L-arginine, is used in lieu of ammonium hydroxide as a pH buffering agent.
In another embodiment, during the reaction of the zinc oxide in the buffered water, the zinc oxide complex undergoes an endothermic reaction and benefits from chilling at a temperature less than 20 degrees centigrade for a period of between about one hour and about 36 hours, preferably greater than 24 hours.
In another embodiment the zinc oxide complex is dried and rinsed with an aqueous solution buffered with, for example, sodium bicarbonate after the 24 hour cooling period to ensure that all excess ammonia is removed, thus ensuring that the zinc oxide complex is highly stable.
In another embodiment the zinc oxide complex physically comprises a creamy white paste, a semi-solid white cake-like consistency or a solid white powder or block throughout the different stages of drying.
In another embodiment an emollient, preferably glycerine is added to the dried zinc oxide complex to improve the physiochemical stability of the product.
In another embodiment an emulsifier such as cetearyl alcohol, cetearyl glucoside such as TEGO® Care CG 90 supplied by Evonik Industries AG, sodium stearoyl glutamate such as Eumulgin® SG supplied by Cognis Corporations, or a combination of cetearyl alcohol and cetearyl glucoside such as Emuglade® PL 68/50 supplied by Cognis Corporation or a combination of Emuglade® PL 68/50 and Eumulgin® SG is added to the zinc oxide complex to form a fully dispersed zinc oxide complex with unsurpassed UVA spectral absorption stability which also exhibits high SPF values.
In another embodiment the emulsifier used in the zinc oxide complex is at least one glucoside emulsifier selected from the group consisting of cocoyl glucoside, cocoyl glucoside/cetearyl alcohol, cocoyl ethyl glucoside, disodium coco-glucoside citrate, lauryl glucoside, disodium coco-glucoside sulfosuccinate, lauroyl ethyl glucoside, myristoyl ethyl glucoside, octyl dimethicone ethoxy glucoside, oleoyl ethyl glucoside, sodium coco-glucoside tartrate, and any mixtures thereof.
In another embodiment the emulsifier used in the zinc oxide complex may include at least one or more additional emulsifiers selected from the group consisting of: butylated PVP, cetyl alcohol, sodium acrylate/sodium acryloyldimethyltaurate copolymer, diethylhexyl napthalate, sorbitan oleate, sorbitan sesquioleate, sorbitan isostearate, sorbitan trioleate, polyglyceryl-3-diisostearate, polyglycerol ester of oleic/isostearic acid, polyglyceryl-6 hexaricinolate, polyglyceryl-4-oleate, polygylceryl-4 oleate/PEG-8 propylene glycol cocoate, oleamide DEA, sodium glyceryl oleate phosphate, hydrogenated vegetable glycerides phosphate and additional emulsifiers selected from the group consisting of: butylated PVP, cetyl alcohol, sodium acrylate/sodium acryloyldimethyltaurate copolymer, diethylhexyl napthalate, and any mixtures thereof.
In another embodiment the zinc oxide complex may include the addition of sodium stearoyl glutamate, such as Eumulgin® SG, sodium N-stearoyl L-glutamate, dioctyldodecyl stearoyl glutamate, TEA-cocoyl glutamate, TEA-lauryl glutamate, TEA-stearoyl glutamate, aluminum stearoyl glutamate, monosodium glutamate, disodium glutamate and any mixtures thereof.
In another embodiment adding an emollient or emulsifier to the zinc oxide complex improves the UV spectral absorption stability.
In another embodiment the emulsifier used is heated to a temperature between about 60 and about 100 degrees centigrade before being added to the zinc oxide complex.
In another embodiment the zinc oxide complex is heated to a temperature of between about 60 and about 100 degrees centigrade to allow for the addition of the chosen emulsifier without preheating the chosen emulsifier.
In another embodiment the zinc oxide complex reflects or absorbs all UVB radiation from about 290 nanometers (nm) to about 320 nm without any degradation in spectral absorption thus allowing for complete UVB protection.
In another embodiment the zinc oxide complex reflects or absorbs UVA radiation from about 320 nm to about 375 nm without degradation of spectral absorption thus allowing for complete UVA protection.
In another embodiment the zinc oxide based formulation shows a sharp UV spectral absorption band edge at about 375 nm, which corresponds with the spectral optical band gap of zinc oxide.
In another embodiment of the disclosure the zinc oxide complex is incorporated into SPF sunscreen or sunblock products, body care products and cosmetics to provide users with protection from harmful ultraviolet radiation.
In another embodiment of the disclosure includes incorporating the zinc oxide complex into wire and cable insulation to provide the insulation with unparalleled protection from ultraviolet radiation increasing the functional lifetime of the insulation.
In another embodiment of the invention the zinc oxide complex is used in thermoplastics to provide protection across the broad UVA/UVB radiation spectrum and increasing the functional lifetime of the thermoplastic materials and products.
In another embodiment the zinc oxide complex is used in wood and metal coatings to prevent degradation or damage resulting from exposure to ultraviolet radiation.
In another embodiment the zinc oxide complex is applied to materials used in the construction of various aircraft parts and car dashboards to prolong their appearance and prevent a decrease in their functionality as a result of damage from ultraviolet radiation.
In another embodiment the zinc oxide complex is used in woven and non-woven textiles, such as clothing and window drapes, to convey heat absorption and UVA/UVB protective properties, as well as provide high SPF values to prevent injury from the sun's rays.
In another embodiment the zinc oxide complex may be used in rubber products and tires in the same manner as carbon black.
In another embodiment, the zinc oxide complex may be incorporated into roofing materials to increase their resistance to the development of cracks and provide adequate insulation and protection from exposure to UVA and UVB rays for the building.
In another embodiment the anti-microbial properties of the zinc oxide complex can be optimized in applications that require such anti-microbial properties.
In another embodiment the zinc oxide complex is provided as a paste or dried powder and functions as a UV stabilizing component for most organic or inorganic compounds.
In another embodiment the zinc oxide complex is provided in paste form and may be used in lieu of UVA/UVB stabilizing compounds or as an alternative to carbon black.
In another embodiment adding carrot oil to zinc oxide complex acts allows for the carrot oil to act as an emulsifier as the carrot oil contains a high concentration of natural glucosides stabilizing the complex.
In another embodiment adding carrot oil to the zinc oxide complex acts as a natural colorant imparting a darker, UV absorbing color to the final product formulations.
In another embodiment the zinc oxide dispersion performs as an exceptional water-resistant barrier and is perspiration resistant. The dispersion has water-resistant properties similar in performance, to Antaron Ganex®, a copolymer of vinylpyrrolidone and long chain alpha-olefins, manufactured by International Specialty Products Inc., however, the ZnO dispersion of the present disclosure is in addition, UV stable, non-toxic to humans and non-endocrine disrupting (the Ganex exhibits none of these attributes).
In another embodiment the zinc oxide complex is added to interior and exterior composite building materials to increase resistance to degradation, discoloration, deformation, and to physical and mechanical stresses due to UV exposure.
In another embodiment the degree of the water-resistant properties can be adjusted by use of different emulsifiers when mixing the zinc oxide dispersion. Emulsifiers include, but are not limited to cetearyl alcohol, sodium stearoyl glutamate such as Eumulgin® SG, cetearyl glucoside such as TEGO® Care CG 90 or a combination of cetearyl alcohol and cetearyl glucoside such as Emuglade® PL 68/50 or a combination of Emuglade® PL 68/50 and Eumulgin® SG. The use of Phospolipon® 90G supplied by American Lechithin Company in Oxford, Conn. and other phospholipids and phosphotidyl cholines may also be useful emulsifiers.
In another embodiment the mixing and blending characteristics of the zinc oxide complex into other materials can be controlled or adjusted by the use of different emulsifiers during the mixing process. The emulsifier can be chemically matched to the chemical system to which it is added. Emulsifiers include, but are not limited to cetearyl alcohol, cetearyl glucoside, sodium stearoyl glutamate such as Eumulgin® SG, cetearyl glucoside such as TEGO® Care CG 90 or a combination of cetearyl alcohol and cetearyl glucoside such as Emuglade® PL 68/50 or a combination of Emuglade® PL 68/50 and Eumulgin® SG.
It is well documented that human skin, and most mammalian skin, is sensitive to sunlight and artificial light containing radiation of wavelengths between about 290 nanometers (nm) and about 400 nm. Ultraviolet radiation of wavelengths between about 290 nm and 320 nm (UVB region) has been known to rapidly produce damaging effects on the skin including reddening or erythema, edema, blistering or other skin eruptions in more severe cases. Prolonged or chronic exposure to radiation in this wavelength range has been associated with serious skin conditions such as actinic keratoses and carcinomas. In recent years, concern has also been expressed regarding ultraviolet radiation of wavelengths above 320 nm (UVA region) and the adverse effects of such radiation on human skin. The radiation between 320 nm and 400 nm also contributes to the premature aging of the skin and also has been implicated in causing DNA mutation. In addition, recent studies indicate that chronic sun exposure limits the immune capabilities of the skin. There is some evidence that a tan will offer some protection against burning, but that the tan is quite ineffectual against many other types of solar damage, and there is no evidence that a tan increases the immune function of human skin Protection against UVC radiation is generally not a major concern, i.e., in contrast to the dangers posed by UVA and UVB radiation.
A study by Margaret Schlumpf from the Institute of Pharmacology and Toxicology at the University of Zurich supports earlier health concerns regarding the use of endocrine disrupting organic substances in nearly all UV screening chemicals used in sunscreens.
Chemical sunscreens contain from about 3% to about 26% of one or more UV-absorbing chemicals. When applied to the surface of the skin as a thin film, for example, about 10 um to about 15 um thickness, these chemicals act as a filter to diminish the penetration of UV radiation to the cells of the epidermis. These sunscreens are typically applied as a cream, oil, lotion, alcohol, spray or gel vehicle and they are usually colorless because they do not contain any visible light-absorbing chemicals. The most widely used chemical sunscreens contain, for example, para-aminobenzoic acid (PABA), PABA esters (glyceryl PABA, amyldimethyl PABA and octyldimethyl PABA), benzophenones (oxybenzone and sulisobenzone), cinnamates (octylmethoxy cinnamate and cinoxate), salicylates (homomethyl salicylate) and anthranilates.
It is desirable to provide a UV protective product that has the following attributes: protection in the UVA and UVB long range and short range ultraviolet radiation ranges; maintenance of coverage, such as, waterproof or at least water-resistant and perspiration proof; application and use convenience, such as, ease of application, invisibility or at least semi-transparency, non-staining and non-greasy; cytoprotective, anti-oxidative and immuno-enhancing properties; and freedom from irritation as a result of its ingredients, in particular, its active sun-block or sunscreen ingredients should also be void of any known or suspected endocrine disrupters.
Physical sunscreens, a compound typically suspended in a cream or lotion, on the other hand, comprise UV-absorbing particles that are relatively physiologically inert. Materials frequently utilized for this purpose include kaolin, talc and two metal oxides; titanium dioxide and zinc oxide, as well as silica and some hydroxides of metals such as aluminum hydroxide. The titanium and zinc oxides are not associated with inflammatory skin reactions.
The physical sunscreen products are, however, typically messy and occlusive. Moreover, they form a visible, opaque, colored (such as white) layer on the surface of the skin, which is cosmetically unacceptable to many who are in need of sunscreen protection. This causes many such individuals to forego the use of these products. The color of these compositions is attributable to the optical properties of the particles from which these materials are formed. These properties are at least partially dependent upon the size of these micronized particles, which typically have a fairly “standard” range of diameters, measured in tenths of a micron, for example, about 0.1 μm to about 0.9 μm.
One current measure of effectiveness of a sun protective product is indicated by its sun protection factor (SPF). The sun protection factor is the ratio of the amount of exposure or dose required to produce minimal erythema in protected skin to the amount of exposure required to produce the same reaction in unprotected skin. The absolute dose differs for each human and for each mammal, and is largely dependent on genetic predisposition and ethnic origin of the human. If a human or other mammal would normally require ten minute exposure to sunlight to develop a minimal erythema reaction, then using an SPF 15 sunblock should allow for tolerance of up to 150 minutes of sunlight before developing a minimal erythema. Relatively recent public awareness of the problems of exposure to sunlight has led to a demand for sunblock products with high SPF values, i.e., at or above SPF 8.
Greater public awareness of the harmful effects of exposure to excessive solar radiation has therefore resulted in an increased use of sunscreen products by the public, coupled with a call for improved sunscreen materials free of the drawbacks described above by those whose livelihood and/or leisure activities cause them to be exposed to any solar radiation. The newly proposed FDA requirements will include UVA stability verification. These requirements will supersede the current FDA monograph issued in 1978.
One study, entitled “In vitro assessments of UVA protection by popular sunscreens available in the United States” by Steven Q. Wang, M D, A Joseph W. Stanfield, M S, and Uli Osterwalder, MSc, illustrates the need for a sunscreen with improved UVA protection capabilities. Its objective was to assess in vitro the degree of UVA protection provided by 13 popular sunscreen products that are commercially available in the United States accomplished through assessment of the 13 products according to the FDA Proposed Amendment of Final Monograph (Aug. 27, 2007), the European Commission Recommendation—the Colipa and critical wavelength methods, and the United Kingdom's Boots star rating system. The results showed that based on the new FDA-proposed guidelines, 8 products achieved the medium protection category, and 5 products achieved high protection. The latter 5 products also fulfilled the UVA protection based on the Colipa guideline desired by the European Commission Recommendation. Nine products achieved the desired critical wavelength value of 370 nm or higher. Based on the United Kingdom's Boots star rating system, 6 products achieved a rating of 3 stars, and the remaining 7 products achieved no star rating. The study concluded that the majority of the tested sunscreens offered a medium degree of UVA protection. Compared with the sunscreens in the past, this study shows that UVA protection of sunscreens has improved while still indicating that improved protection is desired.
Other examples of relevant art are described below:
U.S. Pat. No. 5,587,148 to Mitchell, Kim, et al., and assigned to SunSmart, Inc., describes a topical sunblock formulation for shielding skin from ultraviolet radiation comprising a substantially colorless dermatologically acceptable liquid carrier and micronized particles of zinc oxide containing some lead, arsenic, cadmium, and mercury. The particles are uniformly dispersed in the liquid carrier to form the sunblock formulation in an amount sufficient to protect the skin from hazardous effects of UVA and UVB radiation.
U.S. Pat. No. 5,562,897 to Mitchnick, Mark, et al., and assigned to Silitech Inc. and SunSmart, Inc., describes a process for protecting the skin from the sun's ultraviolet rays in which an effective protecting concentration of a hydrophobic titanium dioxide, prepared by the reaction of a silicone compound conforming to a specific structure with titanium dioxide, is applied to the skin.
U.S. Pat. No. 5,536,492 to Mitchnick, Marck, et al., and assigned to Silitech, Inc. and SunSmart, Inc., describes a process for protecting the skin from the sun's ultraviolet rays in which an effective protecting concentration of a hydrophobic zinc oxide, prepared by the reaction of a silicone compound conforming to a specific structure with zinc oxide, is applied to the skin.
U.S. Pat. No. 5,531,985 to Mitchell, Kim, et al., and assigned to SunSmart, Inc., describes a substantially transparent topical sunblock formulation for shielding skin from ultraviolet radiation comprising a plurality of particles of a visibly transparent UV absorbing crystal glass free of fractures and imperfections dispersed within a substantially colorless dermatologically acceptable liquid carrier in an amount effective to shield the skin from the hazardous effects of ultraviolet radiation.
EP 0935959B1 to Gers-Barlag, Heinrich, et al., and assigned to Beiersdorf Aktiengesellschaft, describes the use of beeswax for increasing the UVA protection performance of cosmetic or dermatological preparations comprising at least one customary UVA filter substance and/or one broadband filter substance which also affords protection against UV radiation with a wavelength greater than 335 nm.
World Patent Application WO 2008108756A1 to Guerry Grune, and not assigned, describes a formulation comprising a combination of at least one inorganic sunblocking or sunscreen agent that is non-endocrine disrupting, at least one emollient that is non-endocrine disrupting, and an oil component capable of protecting skin from the harmful effects of radiation, both sunlight and ultraviolet light. The oil is a carrier oil, an essential oil, or both.
U.S. patent application No. 20090185991A1 to Spaulding, Laura A., et al., and assigned to Playtex Products, Inc., describes a photoprotective composition comprising a synergistic triplet combination of zinc oxide, styrene/acrylate copolymer, and glycol. The synergistic triplet combination conveys a higher SPF value to the photoprotective composition compared to a similar composition that does not include the triplet combination.
U.S. Pat. No. 6,544,530 to Friedman, Doron, and assigned to J.P.M.E.D., Ltd., describes a topically applicable stable oil-in-glycerin composition comprising a continuous glycerin phase, at least one vegetable oil, at least one biodegradable emulsifier, and at least one bioactive essential oil component for topical, external use on skin and mucosal surfaces. The bioactivity of this latter component is selected from the group consisting of topical anti-inflammatory activity, topical anti-fungal activity, topical anti-bacterial activity, topical anti-parasitic activity, and topical anti-viral activity. The essential oil is a volatile mixture of esters, aldehydes, alcohols, ketones, and terpenes.
U.S. Pat. No. 5,340,567 to Cole, Curtis A., et al., and assigned to Johnson and Johnson Consumer Products, Inc., describes a sunscreen composition comprising an extending medium and a synergistic combination of titanium dioxide and zinc oxide present in a weight ratio of from about 1:25 to 10:1. The total of the titanium dioxide and zinc oxide is between about 4.0% to about 25.0% by weight of the total composition.
U.S. Pat. No. 5,916,542 to Fossati, Antonio, and not assigned, describes an antisolar screening and antierythema mixture made of natural substances efficient against damaging UV rays. The mixture comprises amino acids, such as tryptophan, histidine, and phenylalanine, vitamins or provitamins, such as vitamins B6, A, and E, tocopherols, and bioflavonoids, nucleoderivatives, such as nucleosides, nucleotides, and uric acid, and vegetable extracts, such as carrots, bilberry, and aloe.
U.S. Pat. No. 5,945,090 to Randall, William B., et al., and assigned to Randall Products International, describes a quick-drying, waterproof, non-slip sunscreen composition with 1% to 41% by weight of at least one UVA and one UVB component, 1% to 6% stryrene acrylates copolymer, 1% to 49% tapioca powder, and 1% to 4% macrocystis spyriferae algae extract and aloe barbadensis Miller.
German Patent Application No. DE3642794A1 to Iwaya, Katsuma, et al., and assigned to Kao Corp., Tokio/Tokyo, JP, describes a cosmetic composition for preventing sunburn which contains 1% to 25% zinc oxide of a particle size of 70 um to 300 um. It further indicates that the composition may also contain titanium dioxide of a particle size of 30 um to 70 microns um. This composition is undesirable due to its whiteness characteristics when applied to the skin concurrent with high SPF levels.
EP 0619999A2 to Dahms, Gerb Herbert, and assigned to Tioxide Specialties Limited, describes a process for preparing sun protection compositions in which an aqueous dispersion of a particulate metallic oxide is mixed with an emulsifier and an oil phase to form an oil-in-water emulsion and also with a hydrophobic organic sunscreen. The amount of metallic oxide present in the emulsion is up to 10% by weight and the amount of hydrophobic organic sunscreen present is up to 7% by weight. This process produces a composition with a higher SPF than would be expected with an additive effect produced by the quantities of metallic oxide and organic sunscreen used.
U.S. patent application No. 20060008427A1 to Dueva, Olga V., et al., and assigned to Playtex Products, Inc., describes a photoprotective composition comprising a synergistic combination of at least one sunscreen agent and at least one carotenoid, The combination results in a higher SPF value for the photoprotective composition than a similar photoprotective composition without the combination.
U.S. patent application No. 20030215522A1 to Johnson, Eric Scott, et al., and assigned to The Procter and Gamble Company, describes a composition comprising an effective amount of a zinc containing material with an aqueous solubility within the composition of less than about 25% by weight at 25 degrees centigrade, between 5% and 50% of a surfactant, and between 40% and 96% water. The pH of the composition is greater than 7.
U.S. patent application No. 20060280702A1 to SenGupta, Ashoke K., et al., and assigned to AMCOL International Corporation, describes a stable, oil-in-water emulsion-based sunscreen composition with at least one water-insoluble, organic UV-absorber with a water-solubility of less than 0.1% by weight, contained in the oil phase of the sunscreen emulsion comprising zinc oxide particles with no prior coating dispersed in the water phase of the sunscreen emulsion, at least one non- or low-foaming, non-cationic, hydrophilic polymer, capable of dispersing or deflocculating the zinc oxide particles but incapable of thickening an aqueous composition to a viscosity of greater than 100 cps at 25 degrees centigrade, at least one phenolic polymer capable of functioning as a dispersing or deflocculating agent for particulate material, and a buffering agent for the water phase of the sunscreen emulsion.
U.S. Pat. No. 6,264,961 to Ansmann, Achim, et al., to Henkel Kommanditgesellschaft auf Aktien, describes an oil-in-water emulsifier composition comprising an alkyl or alkenyl oligoglycosides, a fatty acid N-alkyl polyhydroxyalkylamide, or an acyl glutamate, and a polyol polyhydroxystearate with a ratio by weight of 90:10 to 10:90.
An article entitled “In Vitro and In Vivo Estrogenicity of UV Screens” by Margaret Schlumpf and others published in Environmental Health Perspectives in March, 2001, confirms that many current UV-protection products may pose health concerns in the form of endocrine disruption, especially in relation to endocrine functions in reproduction and development.
The present invention provides for a zinc oxide based aqueous dispersion for high SPF formulations that shield skin from ultraviolet radiation, having an effective amount of distilled water utilizing a basic pH buffering agent such as ammonium hydroxide, L-arginine or sodium hydroxide, and a zinc oxide powder or solid which is dispersed in a base of a polyol or a glucoside, or other Ecocert® certified emulsifiers or emollients. The dispersion is produced from zinc oxide and buffered water by ensuring that the pH of the water remains above 10.0 during the dispersion reaction of the zinc oxide. The fully reacted zinc oxide dispersion creates pinhole free films providing unexpectedly high SPF values due to exceptionally uniform film coverage.
An embodiment of the disclosure is to provide a zinc oxide based dispersion with high SPF values for use in UVA and UVB radiation resistant sunscreen and sun-blocking compositions.
In another embodiment the zinc oxide based SPF complex is composed of natural-based, earth-grown ingredients which at least meet Ecocert® certifications, and are non-toxic, non-endocrine disrupting, cytoprotective, anti-oxidative and immuno-enhancing substances.
In another embodiment the zinc oxide based dispersion contains chemically stable micronized zinc oxide with or without surface treatments.
In another embodiment the zinc oxide based dispersion exhibits an SPF value of up to about 460 as determined by in vitro testing using a Labsphere UV 2000S Ultraviolet Transmittance Analyzer, available from Labsphere of North Sutton, N.H.
In another embodiment during the reaction of the zinc oxide in the buffered water, the dispersion undergoes an endothermic reaction and benefits from chilling the dispersion at a temperature less than about 20 degrees centigrade.
In another embodiment an ammonium hydroxide (NH4OH) buffer solution is added to distilled water to attain a pH of preferably between about 10.0 to about 11.0 before adding zinc oxide to the water to avoid zinc hydroxide formation by continuously adding zinc oxide until the pH is near 10, not allowing the pH to drop below 10 and then adding more ammonium hydroxide buffer solution to raise the pH and adding zinc oxide to reduce the pH until has all the desired zinc oxide has fully reacted, with a desired pH end point of greater than 9.5.
In another embodiment the dispersion of buffered distilled water and zinc oxide must be allowed to react at a temperature of less than 20 degrees centigrade for between about one hour and about 36 hours, preferably greater than 24 hours.
In another embodiment the zinc oxide dispersion physically comprises a creamy white paste, a semi-solid white cake-like consistency or a solid white powder or block during the different stages of drying.
In another embodiment the zinc oxide based dispersion is washed and dried into a semi-solid white cake-like consistency to remove moisture and then rinsed with alkaline distilled water prepared with sodium bicarbonate brought to a pH of about 7.5 to about 8.5 before re-drying for between about one hour and about 36 hours. The zinc oxide based dispersion then is formed with glycerine or other polyols, emulsifiers or emollients additions (a minimum of 1.0 wt. %) and allowed to stay fully dispersed in the glycerine base preferably greater than 24 hours before compounding with other sunscreen formulation components.
In another embodiment an emulsifier such as cetearyl alcohol, cetearyl glucoside, sodium stearoyl glutamate such as EUMULGIN® SG supplied by Cognis Corporation or a combination of cetearyl alcohol and cetearyl glucoside such as EMUGLADE® PL 68/50 supplied by Cognis Corporation or a combination of cetearyl alcohol and cetearyl glucoside such as EMUGLADE® PL 68/50 and sodium stearoyl glutamate such as EUMULGIN® SG is added to the zinc oxide dispersion to form a fully dispersed zinc oxide compound with inherent UV stability and high SPF values.
In another embodiment adding an emollient or emulsifier to the zinc oxide based dispersion improves the UV stability.
In another embodiment adding an emollient or emulsifier with the zinc oxide based dispersion and allowing to react for between about one hour and about 36 hours, preferably greater than 24 hours produces an exothermic reaction.
In another embodiment adding carrot oil to the fully dispersed zinc oxide based compound decreases the pH wherein adding L-arginine increases the pH to a value greater than about 9.
In another embodiment adding carrot oil to the fully dispersed zinc oxide based compound provides a natural colorant emulsifier with a high concentration of natural glucosides as well as an additional SPF boost by imparting a darker, UV absorbing color to the final SPF formulations.
In another embodiment adding carrot oil to the fully reacted dispersed zinc oxide based compound is preferred when the dispersion includes glycerine.
In another embodiment the zinc oxide based SPF formulation reflects or absorbs all UVB radiation from about 290 nm to about 320 nm without degradation in the UV absorption spectra or in UVB protection.
In another embodiment the zinc oxide based SPF formulation reflects or absorbs UVA radiation from about 320 nm to about 375 nm without degradation in the UV absorption spectra or in UVA protection.
In another embodiment the emulsifier in the fully dispersed zinc oxide based compound contains an emulsifier composition of cetearyl alcohol and cetearyl glucoside such as EMUGLADE® PL 68/50.
In another embodiment the emulsifier used to provide zinc oxide based SPF formulations is at least one glucoside emulsifier selected from the group consisting of cocoyl glucoside, cocoyl glucoside/cetearyl alcohol, cocoyl ethyl glucoside, disodium coco-glucoside citrate, lauryl glucoside, disodium coco-glucoside sulfosuccinate, lauroyl ethyl glucoside, myristoyl ethyl glucoside, octyl dimethicone ethoxy glucoside, oleoyl ethyl glucoside, sodium coco-glucoside tartrate, and any mixtures thereof.
In another embodiment the emulsifier used to provide zinc oxide based SPF formulations is at least one or more additional emulsifiers selected from the group consisting of: butylated PVP, cetyl alcohol, sodium acrylate/sodium acryloyldimethyltaurate copolymer, diethylhexyl napthalate, sorbitan oleate, sorbitan sesquioleate, sorbitan isostearate, sorbitan trioleate, polyglyceryl-3-diisostearate, polyglycerol ester of oleic/isostearic acid, polyglyceryl-6 hexaricinolate, polyglyceryl-4-oleate, polygylceryl-4 oleate/PEG-8 propylene glycol cocoate, oleamide DEA, sodium glyceryl oleate phosphate, hydrogenated vegetable glycerides phosphate and additional emulsifiers selected from the group consisting of: butylated PVP, cetyl alcohol, sodium acrylate/sodium acryloyldimethyltaurate copolymer, diethylhexyl napthalate, and any mixtures thereof.
In another embodiment the zinc oxide based SPF formulations may include the addition of sodium stearoyl glutamate such as EUMULGIN® SG, sodium N-stearoyl L-glutamate, dioctyldodecyl stearoyl glutamate, TEA-cocoyl glutamate, TEA-lauryl glutamate, TEA-stearoyl glutamate, aluminum stearoyl glutamate, monosodium glutamate, disodium glutamate and any mixtures thereof.
In another embodiment the zinc oxide based SPF formulations may be used in a variety of cosmetic and body care products including lipsticks, eye-shadows, foundations, moisturizers, rouges and the like to prevent damage to underlying skin by the action of solar UV radiation.
In another embodiment the zinc oxide based SPF formulations may be used as a component within sunscreen, cosmetic or body care formulations providing unsurpassed UVA/UVB stability between about 290 nm and about 375 nm.
In another embodiment the zinc oxide based SPF formulations contain many components that are known to impart dermalogical healing properties such as anti-inflammatory or anti-microbial effects when topically applied to skin. These components include, but are not limited to zinc oxide, together with aloe and vitamin E.
In another embodiment the zinc oxide used for SPF formulations performs as an exceptional water-resistant barrier and is perspiration resistant. It has water-resistant properties similar in performance, to Antaron Ganex®, a copolymer of vinylpyrrolidone and long chain alpha-olefins, manufactured by International Specialty Products Inc., but is in addition UV stable, non-toxic and non-endocrine disrupting.
In another embodiment the zinc oxide based formulation shows a sharp UV spectral absorption band edge at about 375 nm, which corresponds with the spectral optical band gap of pure zinc oxide.
In another embodiment cornstarch or arrowroot powder or both added to the zinc oxide based formulation increase UV absorption providing an additional SPF boost by reducing the number of pinholes when the zinc oxides based formulation is applied as a thin film and also improving the physiochemical bonding all the constituents in the formulation.
In another embodiment it has also been found that the addition of carrageen and aloe is useful in stabilizing the final formulations and improving film-forming properties.